Nearly 25% of U.S. men aged 55 or older served in combat, yet its impact on aging is unknown. The relationship of posttraumatic stress disorder (PTSD) symptoms to combat exposure was examined in 1,210 veterans of World War II (WWII) and the Korean War, who were participants in the Normative Aging Study. Over 54% of WWII and 19% of Korean veterans reported combat experience. The relationship between combat exposure and PTSD symptoms was stronger in the WWII cohort. The sample prevalence of PTSD by combat exposure ranged from 0% to 12.4%, differing by the PTSD measure. WWII veterans exposed to moderate or heavy combat had 13.3 times greater risk of PTSD symptoms measured 45 years later, compared with noncombat veterans. It is suggested that military service in general, and combat exposure in particular, is a "hidden variable" in the study of aging men.